This disclosure generally relates to providing improved cooling air flow.
Some computer systems, such as blade-based servers, routers, and switches, include a number of hardware cards connected to a hardware plane backbone. The hardware plane is a backplane or midplane typically implemented as a printed circuit board (PCB) with various connectors and components for interconnecting hardware cards to allow for data transfer. A hardware plane may be part of an electronics chassis located in a server rack or a computer case. The hardware cards provide various functionality to the computer systems, such as additional processing, graphics processing, network connectivity, or resource management. During operation of the computer system, the hardware plane and the hardware cards may generate a significant amount of heat. This heat may significantly increase the rate of processor errors and/or equipment failures. A common solution for reducing the generated heat is to use fans to move cooling air around the hardware plane and the hardware cards.
Unfortunately, many existing hardware plane designs prevent efficient air flow around the interconnected hardware plane and hardware cards. For example, existing backplanes have connectors mounted on one major surface of the backplane, with each hardware card connecting to the backplane by an edge orthogonally to one surface of the backplane. Similarly, existing midplanes have connectors mounted on two continuous surfaces with hardware cards connecting orthogonally to either of the two major surfaces of the midplane. Typically, fans may be positioned to direct air orthogonally towards either of the two major surfaces of a hardware plane (i.e. “front to back” or “back to front”). Alternatively, fans may also be positioned to direct air across either of the two major surfaces of the hardware plane (i.e. “side to side”). If a fan is positioned “front to back” or “back to front,” then the air flow is physically impeded by the surface of the hardware plane itself and thus provides less effective cooling. Positioning a fan “side to side” would improve the air flow, but extra lateral space inside the computer system would have to be provided to accommodate the fan.
An additional consideration involved in designing a hardware plane that improves air flow around the hardware plane is determining where to position the data buses, control buses, and connectors on the surface of the hardware plane. Often, at least two types of hardware cards, such as line cards and processor cards, are connected to a hardware plane. Line cards generally connect the hardware plane to one or more telecommunications networks, and processor cards generally send commands to control the line cards and process data received from the line cards. Multiple line cards are connected to the same data bus so that any line card connected to the bus can communicate with any other line card connected to the bus. In addition, each processor card and each line card is connected to the same control bus so that any processor card can communicate with any other processor card, and so that any processor card may send commands to, and receive data from, any line card. Because data and control buses are typically implemented as electrically conducting wires, a hardware engineer carefully plans the layout data and control buses on a hardware plane so that the wires do not physically touch each other. If there is a location on the surface of the hardware plane where two wires would intersect, the hardware engineer can add a physical layer to the hardware plane between the wires so that the wires do not intersect. A location where two wires are prevented from intersecting by a physical layer will be referred to as a wire overlap site. Unfortunately, adding layers to a hardware plane creates a thicker, more complicated, and more expensive hardware plane. Accordingly, it is important to carefully position data buses, control buses, and hardware card connectors on a hardware plane to limit the number of wire overlap sites while allowing the hardware plane to accommodate as many hardware cards as possible.